Metal shutters

One of the technical areas in which Konica demonstrated particular innovative genius is research related to the development of camera shutters. The emergence of vertically-travelling metal-blade shutters owes much to research conducted in the 1950s by Konica. The company’s Hi-Synchro shutter mounted in the KonicaFlex prototype and the Konica F (released in February 1960) was developed over a period of seven years. Work on the Hi-Synchro would eventually contribute to the emergence of the famous Copal Square shutter, variations of which are still used today in most digital SLRs.

The desirability of a vertically-traveling metal shutter has to do with the fact that a shutter that travels across the film gate vertically has only 24mm to cover while a Leica-type cloth shutter that runs horizontally needs to cover 36mm. Moreover, the overall mass of all the moving parts in a shutter essentially made of ultra-thin spring-loaded blades is much lower than that of long horizontally-traveling rubberized curtains mounted on revolving drums. The lower inertia that this vertically-traveling shutter mechanism needs to overcome in conjunction with its metal build and its shorter travel distance make for a shutter that is far more robust and durable, can be controlled with greater precision, and needs less maintenance.

The Hi-Synchro shutter of the Konica F had a fastest speed of 1/2000s and a flash synchronization speed of 1/125s. This was a world first (the Canon R2000, which often passes for having been the first, came out eight months later and used a traditional horizontally running cloth shutter). Just what an extraordinary technical feat this was is best illustrated by the fact that, well into the seventies, the fastest shutter speed on most SLRs, including most professional ones, was 1/1000s. There were two catches, however: The Hi-Synchro was mechanically very complex, making servicing difficult; and it was very expensive to manufacture.

Technical diagram of the Hi-Synchro shutter. 
Photo: Shashin Kogyo, no. 87, July 1959, p. 17. (Δ)

To produce a cheaper and simpler metal shutter, Konica and Mamyia, another camera maker, jointly turned to Copal. This Japanese company had long specialized in high-precision timing mechanisms, including leaf shutters, and was entrusted with the task of perfecting a shutter initially designed in 1957 by a private individual. Copal's efforts in this respect were financed by Konica and Mamiya and made extensive use of Konica’s earlier work on the Hi-Synchro shutter. In 1961, Copal introduced the famous Copal Square I shutter – a sophisticated, robust and affordable shutter whose design owed much to Konica’s Hi-Synchro. The first camera equipped with it was the Mamyia-made Nikorex F. It was also used in the Konica FS in 1962.


Copal Square Shutter  (Ө)

Three more years of research and perfection led to the introduction, in 1965, of the famous Copal Square S, reputed the most reliable mechanical shutter ever made and Copal’s most commonly found shutter. It was incorporated into the Konica Auto-Reflex that same year. Later, the Copal Square S was used in a great number of cameras, like the Nikkormat FT, the Ricohflex TLS401, most Cosina-made SLRs, countless Chinon models, and many others.

The Copal Square S was followed by the Copal Square E (electronically controlled) in 1968, used in the Yashica TL Electro X, the Canon EF, the Nikkormat EL, etc.; the CLS (Copal-Leitz Shutter) in 1972, used in the Minolta XE and the Leica R3; and the CCS-M in 1974, used in the Konica Autoreflex TC and T4, and in the Nikon FM. The CCS was the first of a new series of smaller and more reliable Copal shutters.

Thanks to its metal blades and its vertical travel, the Copal Square shutter is very reliable, quick (its blades travel at a speed of 3m/s) and, most importantly, precise and consistent. The American Standards Association (ASA) degree of tolerance for shutters speeds in the 1960s and 70s was within +/-20% for speeds of 1/100s or slower, and +/-30% for speeds over 1/100s. In a July 1969 write-up on the Autoreflex T, the French magazine Photo-Cinéma tested the accuracy of the camera’s shutter, a Copal Square S, and found the following variations from nominal values:

1s = 0.9s (-10%);                 
1/2.2s (+10%);             
1/4.5s (+12.5%);             
1/9s (+12.5%); 
1/15s = 1/17s (+13.3%);     
1/34s (+13.3%);        
1/70s (+16.6%);           
1/125s1/110s (-12%); 
1/250s = 1/250s (-);             
1/480s (-4%);          
 = 1/920s (-8%). 

As one can see, the greatest discrepancy for speeds of 1/125s and slower is 16.6% and the greatest discrepancy for speeds above 1/125s is 8%.

After Nikon developed it further, the Copal Square reached 1/8000s and a top flash synchronization speed of 1/250s (on the Nikon F4). Even though a number of major camera makers (such as Canon, Pentax, Minolta and Olympus) chose to stick with the Leica-type cloth shutter, metallic shutters based on the Copal model and, in some measure, on Konica’s Hi-Synchro, helped popularize the SLR as the camera of choice in the sixties and seventies. It became the standard for 35mm SLR shutters during the seventies and the dominant type of shutter in most SLRs in the eighties.

Copies of the Copal Square shutter have been installed in SLRs as late as the end of the nineties and even Leitz adopted it in the Leica M8. A large portion of today’s digital cameras are also equipped with shutters that can be considered direct descendants of Konica’s Hi-Synchro and the Copal Square shutters that followed it.

The superior shutters found in the Autoreflex cameras were always one of Konica’s stronger selling points. The Copal Square shutters were more dependable – both in terms of lifespan and accuracy – than the cloth shutters found in the cameras sold by many other makers.